1. Field of the Invention
The invention is in the field of organic and medicinal chemistry. In particular, the invention relates to triazines and the use thereof to inhibit lysophosphatidic acid acyltransferase β (LPAAT-β) activity. The invention further relates to methods of treating cancer using said triazines. The invention also relates to methods for screening for LPAAT-β activity.
2. Related Art
LPAAT catalyzes the acylation of lysophosphatidic acid (LPA) to phosphatidic acid. LPA is the simplest glycerophospholipid, consisting of a glycerol molecule, a phosphate group, and a fatty acyl chain. LPAAT adds a second fatty acyl chain to LPA, producing phosphatidic acid (PA). PA is the precursor molecule for certain phosphoglycerides, such as phosphatidylinositol, and diacylglycerols, which are necessary for the production of other phosphoglycerides, such as phosphatidylcholine, and for triacylglycerols, which are essential biological fuel molecules.
In addition to being a crucial precursor molecule in biosynthetic reactions, LPA has recently been added to the list of intercellular lipid messenger molecules. LPA interacts with G protein-coupled receptors, coupling to various independent effector pathways including inhibition of adenylate cyclase, stimulation of phospholipase C, activation of MAP kinases, and activation of the small GTP-binding proteins Ras and Rho. Moolenaar, J. Biol. Chem 28:1294 (1995). The physiological effects of LPA have not been fully characterized as yet. However, one of the physiological effects that is known is that LPA promotes the growth and invasion of tumor cells. It has been shown that the addition of LPA to ovarian or breast cancer cell lines induces cell proliferation, increases intracellular calcium levels, and activates MAP kinase. Xu et al., Biochem. J. 309:933 (1995). In addition, LPA has been shown to induce MM1 tumor cells to invade cultured mesothelial cell monolayers. Imamura et al. Biochem. Biophys. Res. Comm. 193:497 (1993).
Like LPA, PA is also a messenger molecule. PA is a key messenger in a common signaling pathway activated by proinflammatory mediators such as interleukin-1β, tumor necrosis factor α, platelet activating factor, and lipid A. Bursten et al., Am. J. Physiol. 262:C328 (1992); Bursten et al., J. Biol. Chem. 255:20732 (1991); Kester J. Cell Physiol. 156:317 (1993). PA has been implicated in mitogenesis of several cell lines [English, Cell Signal 8: 341 (1996)]. PA level has been found to be increased in either ras or fps transformed cell lines compared to the parental Rat2 fibroblast cell line [Martin et al., Oncogene 14: 1571 (1997)]. Activation of Raf-1, an essential component of the MAPK signaling cascade, by extracellular signals is initiated by association with intracellular membranes. Recruitment of Raf-1 to membranes has been reported to be mediated by direct association with phosphatidic acid [Rizzo et al., J Biol Chem 275:23911–8 (2000)]. Thus, LPAAT, as an enzyme that regulate PA content in cells, may play a role in cancer, and may also mediate inflammatory responses to various proinflammatory agents.